1. Field of the Invention
This invention relates to a pulse width modulated dimming system in a vehicle, and more particularly to an improved dimming system for manually controlling the dimming of the intensity of the light from the panel lamps with respect to full intensity using a pulse width modulated control signal.
2. Prior Art
In many systems, a field effect transistor controls the amount of current routed to the lamps in the instrument panel. A charge pump/voltage doubler network develops power for driving the FET.
In one prior system, a modest frequency pulse width modulated (PWM) signal stimulates the charging of a capacitor in the charge pump circuit. However, in using the modest frequency PWM signal, usually at least an extra inverting transistor circuit must initiate doubling the voltage across the charging capacitor in order to fulfill the charge pump operation and to keep the variable pulse voltage routed to the lamps in synchronization with the VPWM signal from a microcontroller.
Realizing the need to reduce components in a vehicle and keeping cost of components in vehicles at a minimum without sacrificing performance, a search was initiate for various means to provide control over PWM dimming of lamps. This search resulted in the improved PWM dimming system of the present invention.